Problem: $\dfrac{9}{4} - \dfrac{6}{3} = {?}$
$ = {\dfrac{9 \times 3}{4 \times 3}} - {\dfrac{6 \times 4}{3 \times 4}} $ $ = {\dfrac{27}{12}} - {\dfrac{24}{12}} $ $ = \dfrac{{27} - {24}}{12} $ $ = \dfrac{3}{12}$